Hello and welcome to Healthcare Magic. Thanks for your query.
Penicillin typically causes an immediate or a "type 1" hypersensitivity
reaction. This basically means that the reaction occurs immediately, usually within minutes of exposure to the allergen. So, an allergic / hypersensitivity reaction to Penicillin is unlikely to last for weeks together, even after stopping the medication immediately.
It is possible that the allergic reaction
which you are continuously having could be due to some other allergen and the penicillin incident was just a coincidence. This logic is strengthened by the fact that you have been taking penicillin throughout your life and have not had any allergic reaction.
I think that it would be worthwhile to try and find out what other possible allergen - external or internal - could be causing this. In the meantime, for symptomatic relief, you can take an anti-histamine
medication in order to control your symptoms.
In case, this allergic reaction keeps on persisting, then you may need to see a dermatologist
, to have an allergen testing done to determine the possible source of the allergen.
Wish you all the best.
Dr. Sheeba Stephen